Trials measure chickpea/wheat rotation profit
GroundCover™ Issue: 107 | Author: Nicole Baxter
Chickpeas grown in rotation with wheat have become a valuable part of the Swaffer family's cropping program in Central Queensland
The lift in profitability by planting wheat after chickpeas – compared with wheat after wheat – has been demonstrated in trials by the Queensland Department of Agriculture, Fisheries and Forestry (DAFF) on Brendon and Jody Swaffer’s grain and cotton farm in Central Queensland.
The trials on the Swaffer’s 3200-hectare property north of Clermont showed a chickpea/wheat sequence generated an additional $947/ha gross income over two years compared with two successive wheat crops (Table 1).
To test the effects of chickpeas on soil nitrogen levels, subsequent wheat yields and overall income, the Swaffers have hosted a three-year GRDC-funded trial since 2011.Research technician Maurie Conway and extension officer Max Quinlivan, both from Queensland DAFF, ran the trials.
Mr Conway planted wheat and chickpeas side-by-side in 2011, followed by wheat across the whole trial in 2012.
Urea was applied at four different rates (nil, 20 kilograms/ha, 40kg/ha and 60kg/ha of nitrogen) to investigate the impact on yield and protein.
Also applied were high rates of phosphorus (21.8kg/ha), potassium (37.5kg/ha) and sulfur (17.5kg/ha) to ensure nutrient deficiencies did not limit production.
After two years, the trials showed:
- wheat after chickpeas yielded more than wheat after wheat;
- the additional yield averaged 380kg/ha
- (Table 2) across the four nitrogen rates tested (nil, 20kg/ha, 40kg/ha, and 60kg/ha of nitrogen as granular urea);
- taking into consideration the grain prices, and differences in yield and protein (Figure 1), the additional wheat grown on the chickpea/wheat plots was worth an extra $98/ha;
- the combined gross income from the chickpea/wheat sequence (over two years) was $947/ha more than the wheat/wheat sequence;
- the rotational benefit of the chickpea/wheat sequence is due to enhanced nutrient availability after a chickpea crop, suppression of diseases, changes in weed populations and changes in soil structure, among other factors; and
- the yield benefit in wheat from the rotation was equivalent to applying 20kg/ha to 40kg/ha of nitrogen fertiliser.
In 2012, an area adjacent to the trial site was again planted to wheat and chickpeas to provide more confidence in the data and better understand the long-term impact of chickpeas on wheat yields under different growing conditions.
With a recent spike in the number of grain growers planting chickpeas in Central Queensland, Brendon only grows chickpeas on the same paddocks once every three or four years to help guard against the increased risk of ascochyta blight.
Although no spores were detected in the Swaffers’ 2013 crops, Mr Quinlivan found the disease in some of the chickpea crops he has scouted in Central Queensland this season.
“Ideally, growers in Central Queensland should only plant chickpeas in the same paddock once every three years and two preventive fungicide sprays must be applied at three and six weeks after sowing or before a major rain event, regardless of the presence of symptoms,” Mr Quinlivan says.
He also encourages those saving chickpea seed for sowing in 2014 to treat it with a registered fungicide containing Thiram prior to planting.
To help avoid deficiencies in nitrogen, phosphorus, potassium, sulfur or zinc that could limit productivity, Brendon collects soil samples for testing every year to determine the optimum mix of nutrients needed. Since nitrogen is not applied to the chickpeas, funds are available for investment in other nutrients.
Recent research by Dr Mike Bell, principal research fellow at the University of Queensland’s Queensland Alliance for Agriculture and Food Innovation (QAAFI), shows many farms in Central Queensland have phosphorus and potassium concentrated in the topsoil and critically low levels in the subsoil. However, plants cannot access these immobile nutrients when the topsoil is dry, which reduces productivity.
To address this, Brendon uses a chisel plough to plant the chickpeas. The rig is ideal for use in dry conditions because it allows chickpeas, with their long coleoptiles, to be seeded into moist soil at depths of 150 to 200 millimetres when the surface soil is dry.
Mr Quinlivan says deep placement of phosphorus and potassium in the soil has potential residual benefits for three to four years, but he suggests more research is needed to develop recommendations for fertiliser rates, application methods and the potential longevity of residual benefits for growers.
Chickpeas need phosphorus
Brendon says the biggest lesson learnt from the trial was that his chickpea crops need more phosphorus to thrive. In the past, he routinely applied 5kg/ha of phosphorus at planting, but the research findings have prompted him to apply 7 to 8kg/ha of phosphorus (equivalent to 35 to 40kg/ha of SuPreme Z®).
“It was obvious from the trials that if we weren’t using higher phosphorus rates when sowing our chickpeas we were missing out big time,” he says.
More information:Brendon Swaffer,
07 4985 6110,
07 4983 7424,
0418 708 252,
GRDC Project Code DAQ00170
Region North, South, West